Not only are first round pick QBs not guaranteed to succeed, the odds are strongly against it. Even if you limit it to top 10 first round picks, the success rate is pretty horrible. Over the last 15 years, 20 QBs have been taken in the top 10. Five have been good: Manning, McNair, Bledsoe, NcNabb and Vick. Four could be considered mediocre at best: KCollins, Jeff George, CPalmer and BLeftwich. Two are two early to tell, but did nothing impressive last year: Mannign and Rivers. The other nine were horrific failures: Akili Smith, Ryan Leaf, Heath Shuler, Rick Mirer, David Klingler, Andre Ware, Trent Dilfer (well, maybe just sub-mediocre), Tim Couch and Joey Harrington (maybe too early to say horrific).
In other words, the "success" rate is about 25%, with a 25% chance of a mediocre Jay Fiedler/AJ Feeley quality QB, and about a 50% chance of a complete abortion. And again, that's looking at top 10 picks. If you go further down, you start to include the Jim Druckenmillers, Dan McGwires, Cade McNowns . . . . hey, wait a minute, didn't all of these guys have a cup of coffee with the Dolphins? As much as we like to grouse about John Avery, Eric Kumerow, Billy Milner, etc., none of those guys can hold a candle to Leaf, ASmith, Shuler, Klinger or Ware as collossal draft busts.